Public release date: 10-Oct-2013 [ | E-mail | Share ]

Contact: Mary Beth O'Leary moleary@cell.com 617-397-2802 Cell Press

Human skin must cope with UV radiation from the sun and other harmful environmental factors that fluctuate in a circadian manner. A study published by Cell Press on October 10th in the journal Cell Stem Cell has revealed that human skin stem cells deal with these cyclical threats by carrying out different functions depending on the time of day. By activating genes involved in UV protection during the day, these cells protect themselves against radiation-induced DNA damage. The findings could pave the way for new strategies to prevent premature aging and cancer in humans.

"Our study shows that human skin stem cells posses an internal clock that allows them to very accurately know the time of day and helps them know when it is best to perform the correct function," says study author Salvador Aznar Benitah an ICREA Research Professor who developed this project at the Centre for Genomic Regulation (CRG, Barcelona), and who has recently moved his lab to the Institute for Research in Biomedicine (IRB Barcelona). "This is important because it seems that tissues need an accurate internal clock to remain healthy."

A variety of cells in our body have internal clocks that help them perform certain functions depending on the time of day, and skin cells as well as some stem cells exhibit circadian behaviors. Benitah and his collaborators previously found that animals lacking normal circadian rhythms in skin stem cells age prematurely, suggesting that these cyclical patterns can protect against cellular damage. But until now, it has not been clear how circadian rhythms affect the functions of human skin stem cells.

To address this question, Benitah teamed up with his collaborators Luis Serrano and Ben Lehner of the Centre for Genomic Regulation. They found that distinct sets of genes in human skin stem cells show peak activity at different times of day. Genes involved in UV protection become most active during the daytime to guard these cells while they proliferatethat is, when they duplicate their DNA and are more susceptible to radiation-induced damage.

"We know that the clock is gradually disrupted in aged mice and humans, and we know that preventing stem cells from accurately knowing the time of the day reduces their regenerative capacity," Benitah says. "Our current efforts lie in trying to identify the causes underlying the disruption of the clock of human skin stem cells and hopefully find means to prevent or delay it."

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Cell Stem Cell, Janich et al.: "Human epidermal stem cell function is regulated by circadian oscillations."

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Circadian rhythms in skin stem cells protect us against UV rays

Public release date: 10-Oct-2013 [ | E-mail | Share ]

Contact: Michael C. Purdy purdym@wustl.edu 314-286-0122 Washington University School of Medicine

New research has shown that the stomach naturally produces more stem cells than previously realized, likely for repair of injuries from infections, digestive fluids and the foods we eat.

Stem cells can make multiple kinds of specialized cells, and scientists have been working for years to use that ability to repair injuries throughout the body. But causing specialized adult cells to revert to stem cells and work on repairs has been challenging.

Scientists from Washington University School of Medicine in St. Louis and Utrecht Medical Center in the Netherlands report in the new study that a class of specialized cells in the stomach reverts to stem cells more often than they thought.

"We already knew that these cells, which are called chief cells, can change back into stem cells to make temporary repairs in significant stomach injuries, such as a cut or damage from infection," said Jason Mills, MD, PhD, associate professor of medicine at Washington University. "The fact that they're making this transition more often, even in the absence of noticeable injuries, suggests that it may be easier than we realized to make some types of mature, specialized adult cells revert to stem cells."

The findings are published Oct. 10 in Cell.

Chief cells normally produce digestive fluids for the stomach. Mills studies their transformation into stem cells for injury repair. He also is investigating the possibility that the potential for growth unleashed by this change may contribute to stomach cancers.

In the new report, Mills, graduate student Greg Sibbel and Hans Clevers, MD, PhD, a geneticist at Utrecht Medical Center, identify markers that show a small number of chief cells become stem cells even in the absence of serious injury.

If a significant injury is introduced in cell cultures or in animal models, more chief cells become stem cells, making it possible to fix the damage.

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Stomach cells naturally revert to stem cells

TORONTO--(BUSINESS WIRE)--

Using high-frequency ultrasound and special cardiac-assessment software by FUJIFILM VisualSonics, Inc., researchers have been able to implant engineered stem cells into the damaged heart tissue of mice and, over time, observe the regeneration of healthy cardiac rhythms.

Following a heart attack, scarred and infarcted (dead) tissue can interfere with the heart's ability to regain is regular synchronized motion. Findings published in the September Journal of Physiology by Mayo Clinic researchers reveal that, when mice underwent the grafting of stem cellsspecifically, induced pluripotent stem (iPS) cellsinto their damaged hearts, cardiac motion was resynchronized.

"A high-resolution ultrasound revealed harmonized pumping where iPS cells were introduced to the previously damaged heart tissue," says Satsuki Yamada, MD, PhD, first author of the study: Induced pluripotent stem cell intervention rescues ventricular wall motion disparity, achieving biological cardia resynchronization post-infarction (Yamada S, Nelson T, Kane G, et al., Journal of Physiology 591 (17), 4335-4349).

This first-time discovery offers a significant step towards validating the potential in stem cell-based regenerative solutions to cardiac dyssynchrony. It was captured in ultrasound imaging and hard data through "speckle tracking echocardiography" made possible by VevoStrain Advanced Cardiac Analysis Software manufactured by VisualSonics of Toronto, Ontario. This software provides advanced imaging and quantification capabilities for studying sensitive movements in heart muscles and is the only commercial cardiac-strain package optimized for assessing cardiovascular function in preclinical rodent studies.

Dr. Yamada and his co-researchers utilized this highly specialized software during the implantion and observation of the stem cells within the beating mice hearts. The software documented the following:

By analyzing the data (specifically, measuring strain rate and time to peak analyses in systole), researchers were able to confirm that the irregular rhythms were corrected in those hearts engrafted with the iPS cells: homogenous wall motion was recovered; cell-mediated correction of dyssynchrony and discoordination occurred; and abnormal post-infarction ultrasound speckle patterns were normalized.

The VevoStrain software augments high-resolution imaging capabilities of the Vevo 2100 Imaging system manufactured by VisualSonics for preclinical, in vivo research. VisualSonics regularly attends conferences within the medical and scientific research industry, such as the annual American Heart Association (AHA) Scientific Sessions where visitors can see the VevoStrain software tool in action at the company's booth.

To learn more about VevoStrain software, go to: http://www.visualsonics.com/vevostrain.

About FUJIFILM VisualSonics, Inc.

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High-Frequency Ultrasound Confirms Stem Cells Grafted in Beating Mice Hearts Restores Abnormal Rhythms